A Flying Construction Platform

This is a proposal of a construction platform based on Orion technology. It shall be based on the moon, where it is serviced and maintenanced, and shall be used primary at building sites in lunar orbit. It’s technology traces back to the Orion project. Orion was a space ship that was developed theoretically and with smaller prototypes in the 50th and 60th. It had a nuclear pulse engine. This means it provided huge energy and therefore – first – a high specific impulse, and – second – as well a very high thrust. The Orion nuclear engine is the only known propulsion principle, that can offer both at the same time. This is because of the immense nuclear power of atomic bombs. [If you are interested in that topic also have a look on my newer and much more detailed article Flying Platforms with Nuclear Pulse Propulsion]

The Orion space ship, Fig [1]

The fuel is not burned continuously but explodes in descrete pulses. Any second a load detonates just behind the ship. A damping shield transformes the pushes into a continuous movement. This was tested with chemical prototypes in the early 60th and it worked very well. The BBC has made a TV special on the topic of Orion, where You can also see the chemical prototypes [2]. But before a nuclear version could be build, politics changed and the „Treaty banning nuclear weapon tests in the atmosphere, in outer space and under water“ [3] was signed and made it impossible to further develop such a space ship. But this must not be forever. An exception for nuclear space ships as well as fusion power plants on the moon [4] might come one day. The idea of Orion traces back on proposals of Stanislav Ulam [5] in 1946 and first calculations by Frederick Reines [6] in 1947. In 1958 a secrete development project started at General Atomics [7] and was led by Ted Taylor [8] and physicist Freeman Dyson [9]. In 1965 the project ended without building a nuclear prototype.

A typical Orion engine with a 10m diameter pusher shield, about 2000s Isp and 5000t thrust released by nuclear yields of 140t TNT at a 1sec frequency, Fig [1]

The figure we see is a typical Orion engine. It works as follows: Small loads of 0.02kT to 0.14kT are fired by a pneumatic gun through a hole in a pusher shield. The nuclear loads detonate shortly behind the pusher shield and the detonation hits the shield forward. A spring-damper mechanism tranforms the discrete pushes into a continuous forward movement. The frequency of the detonations is 1sec. With any blast the rocket is accelerated at a maximum by 30m/s/s. This is the highest value the damping mechanism can handle. The ship mass is located between 1000t and 4000t [1]. The mass of a single load is between 375kg and 1500kg. Most of the load mass is a propellant that is vapourized by the nuclear plasma, for example tungsten. Only a small fraction of the load is the uranium nuclear bomb, just a little more than the critical mass, rawly 16kg. It’s bomb yield is between 35t TNT and 140t TNT. The specific impulse of the engine is between 2000s or 20,000m/s with a 10m diameter pusher plate and 3000s or 30,000m/s with a 20m diameter pusher plate. That is very high. The latest chemical engines have 470s [10].

The Construction Platform

The construction platform uses a 30m pusher plate with at least 3500s Isp or 35,000m/s. The Isp of the Orion engine depends strongly on the size of the pusher shield, because as many of the nuclear blast is reflected as better. The fuel units consist of a small amount of uranium of about 16kg for producing the nuclear heat and a propellant of about 1.25t. The construction platform uses simple moon stone as propellant. The platform has a empty weight of 1000t. It can carry 2000t payload from the moon to the moon orbit and 1000t payload from earth to lunar surface.

From the Earth to the Moon.

For lifting off from earth to landing on the moon a delta v of 17,000m/s is required. For flying from earth surface into low earth orbit it is 9300m/s for example. For 17,000m/s we get a mass fraction R = exp(17,000/35,000) = 1.63. For 1000t payload and 1000t ship dry-mass we need 1250t fuel. At the beginning the ship is accelerated with 13m/s/s or 1.3g, at the end with 22m/s/s or 2.2g. 1000 loads with a yield of 110 tons TNT each are fired from earths surface to moons surface, this is 1234 tons of normal concrete as propellant plus only 16t uranium.

From the Moon to the Moon Orbit

For lifting from moon to the moon orbit a delta v of 1900m/s is required. This gives a mass fraction R = exp(1900/35,000) = 1.056. For 2000t payload and 1000t ship dry-mass it needs 167t fuel. At the beginning the ship is accelerated with 14m/s/s at the end with 15m/s/s. 133 loads of yield 110t TNT are fired from moons surface to moons orbit, it is 164.9t moon rock propellant plus 2.1 tons of uranium.

For landing on the moon surface the delta v is 2500m/s. The mass fraction R is then 1.074. For landing on the moon without payload the 1000t ship needs 74t fuel. For moon landing manouvres the propellant is as half as big, so it is 609kg moon rock propellant plus still about 16kg uranium. Because the uranium ammount remains nearly the same just above the critical mass. The yield of the nuclear detonator is as half as big as that of the earth flight detonators this is adjusted by removing some ten grams from the uranium detonator. Just above the critical mass the fission bomb yields respond very sensible on adding or removing small amounts of uranium. But it is a well mastered technology, that was once perfected by Ted Taylor [8] and is still used by the military for tactical weapons. And of course the military has to supervise the propulsion units of our construction platforms. When flying back from the moon orbit to the moon surface, at the beginning the ship is accelerated with 20m/s/s at the end with 22m/s/s. 116 nuclear loads with a yield of 55t TNT each are fired with 72.1t moon rock propellant plus 1.9t of uranium.

So for any round trip from the lunar surface to the moon orbit and return to the lunar surface, the platform needs 4t uranium. At it’s maiden flight from the earth to the moon it can carry 1000t uranium fuel with it. This is enough for 250 round trips with 2000t payload or carrying 500,000t payload from the moon to the moon orbit. Yes, with only one single launch from earth the construction platform can carry half a million tons building material from the moon surface to the moon orbit.

A Design Proposal

Here comes my proposal, how such a construction platform could look like. I admit, it doesn’t look like a space ship. It looks more like a offshore platform. But I, personally, don’t wonder about that. Isn’t it actually not a kind of offshore platform, if we picture the moon as a far shore?

A flying construction platform based on the Orion principle, with its own crane, carrying a truck, a (radiation hardened) small piggyback space station and a huge aluminium reinforced concrete part of 2000 tons behind the truck, Fig. Author

Compare this figure with the figure of the Orion engine above. You will find out: this ugly Monstermaschine is also an Orion spaceship. Although it doesn’t look like a spaceship. It’s ugly, it’s built only for pragmatic reasons, and it’s primary purpose is not to bring people to other planets. But it has all what is needed: the pusher plate, the first damping stage for high frequency damping, the long damper colums for damping the yield of the bombs within one second, the pneumatic gun which fires the bombs through a hole in the pusher plate, the bomb containers and tranporting mechanisms inside the platform, and the massive and heavy structures to withstand the hot plasma and the radioactive contamination.

At lift-off, it uses half yield bombs, because the ground effect doubles the pressure on the pusher plate. After some detonations, the platform has flown high enough that it can use its nominal loads and accelerates further. The four landing gears are retracted, that they don’t suffer too much thermal radiative and dynamic-mechanical stress. The thrust vector control is done by means of an active damper viscosity control. The roll control is done by the attitude control system the platform needs in orbit, but it might also be done during flight by giving the bombs a certain rotation rightwise, leftwise or neutral.

The bombs are shot any single second from the little cone in the middle of the bottom side of the platform. That is the muzzle of the pneumatic gun. They fly through a hole in the pusher plate and detonate just a few meters above the ground. The nuclear bombs are so small that all structures can stand their heat and pressure peak on earth. But most of the time the device works on the moon and in space and there is no blast wave, this is why the mechanical loads are relatively small. Vice versa, an additional propellant in the load is used to produce more ionized matter that is blasted onto the pusher plate, to get more pressure from the explosions. This produces a high thrust of 4225t, that moves the pusher plate in half a second 7m to 10m to the platform and then in half a second back.

The platform should only fly one single time from earth: after it was built. Then it flies directly to the moon where it will have it’s home base from now on. On it’s mayden flight it can carry the complete fuel for it’s whole lifetime with it, for carrying half a million tons payload from the moon to the lunar orbit.

The construction platform has its own crane that is able to move single payloads of 333t on earth and 2000t on moon. On the moon the platform must be mounted with additional wire ropes for hauling up such huge loads, otherwise the platform will cant over. In the moon orbit the platform can serve several months as a home base for workers and their building material. Because it is perfectly rectengular, it also can connect with other platforms and form one big construction platform in moon orbit until it is time to fly back to the lunar surface and take over again 2000t building material.

Purpose

There are five good reasons for building such an ugly space ship.

It is providing giant building sites in space with concrete and aluminium parts from the moon. Moon rock is made of anorthosit and anorthosit is made to 90% by volume of anorthit (CaAl2Si2O8) [11]. This means if you have an adequate energy source on the moon, for example fusion bomb energy plants [4], you can melt out aluminium, silicone, calcium and a lot of gaseous oxygen. From this constituent parts it is also possible to make cement. Typical cement is 58 bis 66 % CaO, 18 bis 26 % SiO2, 4 bis 10 % Al2O3 [12], so it shall be no bigger problem to make moon concrete out of powdered moon rock, if you have a method to recycle the water from the process of making concrete parts.

Protecting the earth from comets and asteroids. A small swarm of these platforms moves away comets of any known size in all distances. They can blast the comets into smaller parts and can move all of this parts, or they move the whole comet working together. The Orion engine is the most powerful engine that is physically known. It is the only realistic chance to protect earth from asteroids. All other physically founded methods, do not even have one tenth of a percent of it’s power.

Mining asteroids. You can fly directly to the asteroids with the platform, there you either mine minerals and bring 2000 tons raw ore back to the moon or you even blast the asteroid into smaller parts and tug the parts into the lunar orbit as you would do with the precious water from comets. Whatever, if water from comets or minerals from asteroids, on the moon they would be a hundred times cheaper than to provide them from earth. This is a simple result from the gravitational potential and has nothing to do with distance. There may be many minerals that will be even cheaper to mine from asteroids with this platform than mining on earth. Maybe uranium, gold or others of the more expensive minerals.

Mining comets. It’s the same as with the asteroids. You do this, if you need water ice for the building sites in the moon orbit or for the lunar surface. Tug smaller comet parts to the lunar orbit, or let them fall on the moon via a controlled ditch for building power plants like the Nomad fusion reactors [4] that need a lot of water.

Mars missions. The delta v for a start from moon to a soft landing on mars is 9800m/s. The mass fraction R is 1.33 with 3500s Isp. If we want to land 900t material on mars and want to return with 100t of it, we have to start with 3010 tons lift-off weight on the moon, land with 2263 tons on mars. Here we deploy 800 tons payload for building nuclear power plants, for example. Then we lift-off with 1463 tons from mars and fly directly back to the lunar surface where we land with 1100 tons. Altogether we have burnt 1110 tons fuel, this is 18.9t uranium fuel and 1091.1 tons moon rock.

Problems

This sounds very invitingly, especially the huge payloads and the small amounts of uranium fuel that are needed for them. But there are some big problems with such a construction platform:

The blasts of the bombs are highly radioactive. If astronauts fly with the platform, they have to stay within a massive shelter, a kind of small space station, during the propulsion phases. After the engine is switched off, they have to wait for some days until the radioacitvity of all parts on the platform is fallen below a medically unhesitating level and they can leave their shelter. Some of the parts (e.g. the truck on our figure) should also be protected by thick foils from the radioactive dust. After the platform is landed on the moon again, it has to be decontaminated by sweeping off the radioactive fine dust that the radioactivity doesn’t accumulate with time. Working with the platforms means measuring radioactivity everywhere, anywhere in their vicinity to be safe. All space suits will have integrated Geiger counters and dosimeters to protect the personnel.

At it’s maiden flight the platform has to start from earth. There it pollutes the atmosphere to a certain degree and later the magnetic field of the earth, while flying through it. With it’s ionized plasma it creates it’s own radiation belt like the Van Allen belt, but with uranium fission products, that are very dangerous to health. This radiation belt vanishes after a certain time, and the radioacitvity of the athmosphere is also washed out by rain after some time. But it would be no good idea to start platforms more often than for just one maiden flight to position them at their moon home base. They can carry a lot of uranium fuel with them, when starting from earth, but later they should be refueled by a conventional chemical transportation system from the earth to the moon, like that I have proposed in my last article „Transporting Heavy Duty to the Moon“ [13].

The fuel is actually a kind of nuclear mini-bombs and their might be a certain danger as long they are on earth that terrorists could steal one of the mini-bombs. Such bombs are at least strong enough to blast one skyscraper, so they are still dangerous. Later in space on the moon this danger disappears. But the propulsion personal at the moon base or at the building site in orbit will allways be military personal. This must be sure from the beginning.